Network connections with a high bandwidth are presently required for the rapid transport of medical image data (for example MRT or CT data) in a networked environment. The trend in medical diagnosis is toward methods that, because of higher demands placed on image resolution, require real-time processing of ever larger data volumes, and higher data rates, and this is attended by an increase in network utilization when sending image data.
An optional access to a subset of the image data (for example the first and last frame of an image data sequence comprising a number of frames) is possible only locally, since the entire image (for example according to the DICOM standard) has been transmitted completely. By contrast, it would be desirable to have an optional access to the bulk data (for example to individual frames or a number of pixels of an image) in order, if required, to enable individual data blocks of the image data sequence to be transmitted in an optimized fashion with regard to the network utilization (by contrast with transmission of the complete image data sequence in accordance with the DICOM standard).
US 2003/0005464 A1 describes a client/server system and an associated method for separately storing medical image data (pixels) and meta data (header) in a computer network, the image data being stored in a central data archive without any kind of additional information, and the meta data, including specific generated links to the image data, being stored in a separate, spatially remote data archive. The separated storage is intended in this case to ensure recourse to standard technologies for data storage on a scalable scale, and to ensure compliance with data protection requirements.
US 2002/0023172 A1 discloses a client/server system and an associated routing method for transmitting medical image data and meta data via a packet-switched computer network. Use is made here of a router that evaluates the address information contained in the data packets to be sent, and uses routing tables to determine the most favorable path of the data from a central network server through the network to a client terminal. The system in this case includes the allocation of access keys, so-called “Global Unique Identifiers” (GUIDs), for medical image data. Such a GUID is intended to be used given the presence of a number of copies of an image data record to detect whether a copy is locally available or must be first be downloaded from the central network server. Image data and meta data are treated in this case in a different way.
Since an exemplary embodiment of the present invention refers to a storage and access method that is preferably intended to be used in the field of medical image retrieval, two of the currently predominantly used communication standards for the description, storage, transmission and interpretation of medical image data and of context information allied thereto, namely: DICOM SR (“Digital Imaging and Communication in Medicine—Structured Reporting”) and HL7 (“Health Level Seven”) are briefly presented below.
The communication standard DICOM, whose third part is described in detail in the specialist article “Digital Imaging and Communications in Medicine (DICOM)” (PS 3.3-2003, Rosslyn, Va.) is a standard for exchanging and managing medical image data and other data associated therewith. It was developed in the field of radiology and will in future also be promoted as a standard in all other specialist medical fields.
A DICOM document includes two sections: Header data including the “Report Title” consisting of DICOM code, and the so-called “Document Content Sequence”, which includes the medical data part coded using the SNOMED (“Systemized Nomenclature for Medicine”) standard. SNOMED is a descriptive language with its thesaurus comprising more than 50,000 terms, and is used for coding, indexing and finding data in patient files. Mnemonic, hierarchical, group-sequential, incremental and combination codes belong to the coding schemes used in this case. In addition to SNOMED, the DICOM standard uses numerous further coding schemes (for example ICD or LOINC).
The HL7 CDA standard described in detail in the specialist article “HL7 Clinical Document Architecture Framework” (Release 1.0, 2000) is an international communication standard for the exchange, management and integration of data that are required for patient treatment.
By contrast with unstructured full-text documents, HL7 CDA and DICOM SR documents are distinguished by an explicitly coded document structure that is characterized, for example, by coded chapter and section designations. The context information respectively associated with any data element for which entry is envisaged can be read out in this case from a library file. These items of context information are lost in conventional methods for indexing full-text documents, thus reducing the accuracy of the search process. Consequently, it is not possible to ensure in the case of conventional indexing that a search request will supply all relevant documents for a specific search request.
Structured objects that are stored in the DICOM SR or HL7 CDA format do not themselves contain image objects (including header data and binary-coded image data) but so-called unique identifiers (UIDs) via which image data and other objects (such as biosignal data, for example) are referenced. DICOM SR uses, for example, UIDs, which are used to denote the type and entity of referenced objects. Within the document, these UIDs are in the context of further described data, for example codes, with the aid of which an investigation method is described in more detail. The “content” of a specific referenced object can be described, together with relevant observations, with the aid of these meta data.
Extensions of the O2 query language are known for structured SGML documents and object-oriented databases, as explained in the article entitled “From Structured Documents to Novel Query Facilities”, (SIGMOD RECORD, 23 (2): 313-324, June 1994) by V. Christophides, S. Abiteboul, S. Cluet and M. Scholl. XQuery language, which is described in “XQuery 1.0: An XML Query Language” (W3C Working Draft 2002) and is suitable for information retrieval applications, exists for XML documents; it makes use of XPath language described in the specification “XML Path Language (XPath) Version 1.0” (W3C Recommendation 1999) in order to address parts of an XML document. XPath is capable of selecting document nodes with specification of various criteria, and of carrying out fundamental manipulations on character chains, Boolean values and node sets, and contains a simple function library that can be expanded by means of user-defined functions.
Medical image data are usually sent with the aid of the DICOM protocol via local data transmission networks (for example via the LAN of a hospital) in the case of products that are currently commercially available. In this case, a complete image data sequence which includes, for example, demographic patient data, measurement parameters, image data and conventional examination information (notes, graphics etc.) is serialized, coded and sent via the network. The serialized data stream is decoded at the receiver end and correctly reconstituted so that a local application can then optionally access the data. This means that even frames not required by the receiver are sent along with the data stream.